In the related art, an ultrasonic diagnosis apparatus is relatively small in size as compared with other medical image diagnosis apparatuses such as an X-ray diagnosis apparatus, an X-ray computed tomography (CT) apparatus, and a magnetic resonance imaging (MRI) apparatus and can display the movement state of an examination target such as a heartbeat or the movement of a fetus in real time by the simple operation of making an ultrasonic probe come into contact with a body surface. Thus, the ultrasonic diagnosis apparatuses are playing play an important role in current medical care. Further, developments have been made to the size of the ultrasonic diagnosis apparatuses that have no risks of radiation exposure so that handy-held apparatuses are developed. Such an ultrasonic diagnosis apparatus can be conveniently used in medical practice such as medical care at an obstetrics office or home.
Further, an intravenous ultrasound contrast agent (hereinafter, referred to as a contrast agent) has been recently commercialized, and so a “contrast echo method” has been performed. In the contrast echo method, by enhancing a blood flow signal by injecting a micro bubble or the like as the contrast agent into a vein, blood flow moving state can be clearly observed. For example, the contrast echo method is used for an examination of organs such as the heart or the liver. A doctor can make a differential diagnosis of cancer or a diagnosis of a diffuse liver disease such as chronic hepatitis or cirrhosis with reference to the blood flow moving state visualized in an angiogram generated by the contrast echo method. For example, in the case of primary liver cancer, a doctor can make differential diagnosis as to whether a liver tumor is benign or malignant by using the blood flow information of an arterial phase and blood flow information of a portal phase visualized in an angiogram in a complementary fashion.
As a technique of clearly showing a time-dependent change in intensity of the blood flow signal for observation of the blood flow moving state by using the contrast echo method, there is a known technique of mapping the injection time of the contrast agent on a still image. For example, in the above technique, by representing a difference between peak times of a signal reflected by the contrast agent with a different hue, it is possible to clearly represent the times at which the contrast agent is injected into various portions shown on the same image.
However, in the conventional art, there has been a  case in which it is difficult to discriminate the dominant regions of different vascular channels.